CN112376024B - Preparation method of oxide film - Google Patents

Abstract

The invention discloses a preparation method of an oxide film, which comprises the following steps: putting a wafer to be deposited with a film on a base of a reaction chamber; introducing mixed gas of argon and oxygen into the reaction chamber, applying direct current power and radio frequency power to the target material to enable the mixed gas to form plasma, and bombarding the target material by the plasma to form an oxide film on the wafer; stopping applying power to the target, introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying radio frequency power to the base to enable the mixed gas to form plasma, and bombarding the oxide film by the plasma to form a nitrogen oxide thin layer; and continuously introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying direct current power and radio frequency power to the target, continuously applying radio frequency power to the base, enabling the mixed gas to form plasma, and bombarding the target and the nitric oxide thin layer by the plasma to form a nitric oxide thin film on the nitric oxide thin layer.

Description

Preparation method of oxide film

Technical Field

The invention relates to the field of semiconductor process, in particular to a preparation method of an oxide film.

Background

In recent years, the development of very large scale integrated circuit technology is rapid, the feature size of the device is continuously reduced, the density of the device is continuously increased, and the RC delay caused by the metallization interconnection becomes a key factor that hinders the performance and speed of the very large scale integrated circuit. Therefore, reducing RC interconnect delay has become a leading direction in the semiconductor industry in recent years. In integrated circuit fabrication, metal lines are typically embedded in an interlayer dielectric (ILD) material having a low dielectric constant. In a damascene interconnect process, etch stop layers are typically deposited on the individual ILD layers and metal lines and used in the patterning of the IC fabrication process to protect the materials underlying these layers from being etched during patterning, while the etch stop layers are typically not completely removed and remain as a thin film between the thicker ILD layers in the finally fabricated semiconductor device.

Aluminum oxide is increasingly being used as an etch stop layer due to its good process compatibility. The alumina film is usually prepared by CVD method, but the film has more impurities, low density and high process cost. Compared with the CVD process, the alumina film prepared by the pulsed magnetron sputtering technique is one of the most commonly used Physical Vapor Deposition (PVD) methods in the metallization process of integrated circuits due to its advantages of good film uniformity, less impurities, high density, etc. However, the traditional PVD method has a small process window and increasingly prominent limitations, such as low deposition rate, non-uniform etching, and frequent abnormal arc discharge causing particle defects, which makes subsequent process integration difficult. Therefore, it is highly desirable to find a new method for preparing a thin film.

Disclosure of Invention

The invention aims to provide a preparation method of an oxide film, which solves the problems of low deposition rate, particle defects, large surface roughness and low film density in the process, and comprises the following steps:

step 1: putting a wafer to be deposited with a film on a base of a reaction chamber;

step 2: introducing mixed gas of argon and oxygen into the reaction chamber, applying direct current power and radio frequency power to the target material to enable the mixed gas to form plasma, and bombarding the target material by the plasma to form an oxide film on the wafer;

and step 3: stopping applying power to the target, introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying radio frequency power to the base to enable the mixed gas to form plasma, and bombarding the oxide thin film by the plasma to form a nitrogen oxide thin layer;

and 4, step 4: and (3) continuously introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying direct current power and radio frequency power to the target, and continuously applying radio frequency power to the base to enable the mixed gas to form plasma, wherein the plasma bombards the target and the nitrogen oxide thin layer formed in the step (3) so as to form a nitrogen oxide thin film on the nitrogen oxide thin layer.

In the alternative, the process conditions in thestep 1 are as follows: the vacuum degree of the reaction chamber is less than 5E-6 Torr; the temperature of the base is 250-350 ℃.

In an alternative scheme, in thestep 2 and/or thestep 3, the flow rate of argon is less than 500sccm, and the flow rate of oxygen is less than 500sccm, wherein the flow rate of argon is greater than the flow rate of oxygen.

In thestep 2, the direct current power applied to the target is less than 10000W, the radio frequency power applied to the target is less than 3000W, and the ratio of the radio frequency power to the direct current power is 2-4.

In thestep 2, the direct current power applied to the target is 100-200W, the radio frequency power applied to the target is 300-600W, and the ratio of the radio frequency power to the direct current power is 3.

In thestep 4, the direct current power applied to the target is less than 10000W, the radio frequency power applied to the target is less than 3000W, and the ratio of the direct current power to the radio frequency power is 2-7.

In thestep 4, the direct current power applied to the target is 3000-6000W, the radio frequency power applied to the target is 1000-2000W, and the ratio of the direct current power to the radio frequency power is 3-6.

In an alternative scheme, in thestep 3 and/or thestep 4, the sum of the flow rates of the oxygen and the nitrogen is larger than the flow rate of the argon.

In an alternative, in thestep 3 and/or thestep 4, the radio frequency power applied to the base is less than 500W.

In an alternative, the target comprises an aluminum, titanium, silicon, hafnium or tantalum target, or a compound target comprising aluminum, titanium, silicon, hafnium or tantalum.

The invention has the beneficial effects that:

instep 2, the direct current power and the radio frequency power are simultaneously applied to the target material, so that the generation of particle defects in the oxide deposition process can be reduced. In thestep 3, mixed gas of argon, oxygen and nitrogen is introduced, radio frequency power is applied to the base, a nitrogen oxide thin layer can be generated in situ, certain etching can be performed on the surface of the oxide thin film, and the surface roughness is reduced while the surface defects of the oxide thin film are reduced. Instep 4, the mixed gas of argon, oxygen and nitrogen is continuously introduced, the direct current power and the radio frequency power are applied to the target material, the radio frequency power is applied to the base, a high-density and low-roughness film can be formed on the surface of the wafer in a deposition mode, a transition layer can be formed between the etching layer and the metal on the high-quality surface, and oxidation of the metal layer is reduced.

The method of the present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings.

FIG. 1 is a flow chart illustrating the steps of a method for forming an oxide thin film according to an embodiment of the present invention.

FIG. 2 shows a graph comparing the number of particle defects in oxide thin films prepared according to an embodiment of the present invention and the prior art.

FIG. 3 shows a graph comparing etch uniformity of oxide films prepared according to an embodiment of the present invention and prior art.

Detailed Description

The present invention will be described in more detail below. While the present invention provides preferred embodiments, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

An embodiment of the present invention provides a method for preparing an oxide thin film, and fig. 1 is a flowchart illustrating steps of a method for preparing a thin film in a semiconductor process according to an embodiment of the present invention. Referring to fig. 1, the method for preparing the thin film includes:

step 1: putting a wafer on which a film is to be deposited on a base of a reaction chamber;

step 2: introducing mixed gas of argon and oxygen into the reaction chamber, applying direct current power and radio frequency power to the target material to enable the mixed gas to form plasma, and bombarding the target material by the plasma to form an oxide film on the wafer;

and step 3: stopping applying power to the target, introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying radio frequency power to the base to enable the mixed gas to form plasma, and bombarding the oxide film by the plasma to form a nitrogen oxide thin layer;

and 4, step 4: and (3) continuously introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying direct current power and radio frequency power to the target, and continuously applying radio frequency power to the base to enable the mixed gas to form plasma, wherein the plasma bombards the target and the nitrogen oxide thin layer formed in the step (3) so as to form a nitrogen oxide thin film on the nitrogen oxide thin layer.

To facilitate understanding of the present solution, a brief description will first be given of an apparatus for preparing a thin film. The preparation of the film is carried out in a reaction chamber, a base is arranged in the reaction chamber and used for bearing the wafer of the film to be deposited, and the base has a heating or cooling function. The reaction chamber is connected with a vacuum system, and the vacuum system can exhaust the reaction chamber to ensure that the reaction chamber reaches higher vacuum degree so as to meet the vacuum condition required by the process. Gases (such as argon, oxygen, etc.) required for the process are connected to the reaction chamber through a flow meter, and a target required for the process is sealed in an upper region (above the susceptor) of the reaction chamber. The target material can be pure metal or metal compound, and can also be silicon or silicon dioxide (when silicon oxide is required to be deposited). During the thin film deposition, the power supply applies power to the target material to make the target material be negatively biased relative to the grounded reaction chamber, in addition, the high voltage makes argon and oxygen ionized and discharged to generate positively charged plasma, and the positively charged plasma is attracted by the target material and bombards the target material. When the energy of the plasma is high enough, atoms on the surface of the target material can be escaped and deposited on the wafer, so that the thin film deposition on the surface of the wafer is realized.

In this embodiment, a method for depositing a composite film of aluminum oxide and aluminum oxynitride on a surface of a wafer is taken as an example to describe the preparation method in detail.

Specifically,step 1 is executed, appropriate process conditions are set for the reaction chamber according to different deposited films, a wafer to be deposited with the film is placed on a base of the reaction chamber, and the temperature of the base is adjusted to the temperature required by the process. In the embodiment, the process conditions for depositing the alumina film are set in such a way that the vacuum degree of the reaction chamber is less than 5E-6 Torr; the temperature of the susceptor is in the range of 250 ℃ to 350 ℃, preferably, e.g., 300 ℃.

And 2, introducing mixed gas of argon and oxygen into the reaction chamber, applying direct current power and radio frequency power to the target material to enable the mixed gas to form plasma, and bombarding the target material by the plasma to form an oxide film on the wafer. In the prior art, only pulse direct current power is applied to a target, and because an alumina film is a non-conductive oxide, the pulse direct current power has two stages of positive voltage and negative voltage in one period, in the negative voltage stage, a power supply works in sputtering of the target, and in the positive voltage stage, electrons are introduced to neutralize positive charges accumulated on the target surface. In the process, the deposition rate is low, the etching is uneven, particle defects are caused by frequent abnormal arc discharge, the surface roughness is large, the film density is low, and the subsequent process integration is very difficult due to the fact that impurity gases such as water, oxygen, carbon and the like in the air are easily adsorbed to form surface defects. In this embodiment, the direct current power and the radio frequency power are applied to the target material at the same time, so that the ion energy can be reduced, the damage to the bottom ILD film can be avoided, and the high-density alumina contact layer film can be formed.

And 3, stopping applying power to the target, introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying radio frequency power to the base to enable the mixed gas to form plasma, and bombarding the oxide film by the plasma to perform surface treatment. In the step, radio frequency power is applied to the base, a thin oxynitride layer can be formed in situ, namely a thin oxynitride layer is generated on the surface of the oxide film, certain etching can be performed on the surface of the formed oxide film, and the surface roughness is reduced while the surface defects of the technical oxide film are reduced.

And 4, continuously introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying direct current power and radio frequency power to the target, continuously applying radio frequency power to the base, enabling the mixed gas to form plasma, and bombarding the target and the nitrogen oxide thin layer (or the oxide thin film) formed in thestep 3 by the plasma so as to form the nitrogen oxide thin film on the nitrogen oxide thin layer (or the oxide thin film). In the step, the direct current power and the radio frequency power are applied to the target material at the same time, the radio frequency power is applied to the base, the etching repair and the deposition process of the film are performed at the same time, the deposition rate is greater than the etching rate, so that the high-density and low-roughness film is formed on the surface of the wafer in a deposition mode, a transition layer can be prevented from being formed between the etching layer and the metal on the high-quality surface, and the oxidation of the metal layer is reduced.

In the embodiment, in thestep 2, the process pressure of the reaction chamber is maintained at 3 to 10mTorr, the flow rate of argon is less than 500sccm, and in the preferred embodiment, the flow rate of argon is in the range of 50 to 200 sccm; the flow rate of the oxygen is less than 500sccm, and in a preferred embodiment, the flow rate of the oxygen is in a range of 20 to 100 sccm. In this embodiment, the flow rate of argon is greater than that of oxygen, i.e., the ratio of argon to oxygen is greater than 1. This is in contrast to the prior art (ratio of argon to oxygen is less than 0.5), where too high a ratio of oxygen is detrimental to particle defect and etch uniformity control. The direct current power applied to the target is less than 10000W, and in a preferred embodiment, the direct current power is in a range of 100-200W. The radio frequency power applied to the target is less than 3000W, and in a preferred embodiment, the radio frequency power is in a range of 300-600W. Wherein the ratio of the rf power to the dc power applied to the target is about 3, such as 2 or 3 or 4. The appropriate power ratio can alter the lateral migration of the film as it grows on the substrate surface by increasing the ionization and collision of the aluminum and oxygen atomic high density plasma (when depositing an aluminum oxide film), thereby forming a low damage, high density film without causing damage to the low dielectric constant interlayer dielectric layer of the previous layer, thereby altering the dielectric constant of the material.

In the present embodiment, instep 3, the process pressure of the reaction chamber is maintained at 3 to 10mTorr, the flow rate of argon is less than 500sccm, and in the preferred embodiment, the flow rate of argon is in the range of 50 to 200 sccm; the flow rate of the oxygen is less than 500sccm, and in a preferred embodiment, the flow rate of the oxygen is in a range of 20 to 100 sccm. In this embodiment, the sum of the flow rates of oxygen and nitrogen is greater than the flow rate of argon, that is, the ratio of the sum of the flow rates of oxygen and nitrogen to the flow rate of argon is greater than 1. The RF power applied to the base is less than 500W, and in the preferred embodiment, the RF power applied to the base is in the range of 50-100W. The arrangement mode can carry out certain bombardment on the surface of the film, form a nitrogen oxide aluminum thin layer in situ, reduce surface defects and simultaneously reduce the roughness of the surface.

In the present embodiment, instep 4, the process pressure of the reaction chamber is maintained at 3 to 10mTorr, the flow rate of argon is less than 500sccm, and in the preferred embodiment, the flow rate of argon is in the range of 50 to 200 sccm; the flow rate of the oxygen is less than 500sccm, and in a preferred embodiment, the flow rate of the oxygen is in a range of 20 to 100 sccm. In this embodiment, the ratio of the sum of the flow rates of oxygen and nitrogen to the flow rate of argon is greater than 1. The direct current power applied to the target is less than 10000W, in a preferred embodiment, the direct current power is 3000-6000W, the radio frequency power applied to the target is less than 3000W, in a preferred embodiment, the radio frequency power is 1000-2000W, and the ratio of the direct current power to the radio frequency power is controlled between 2 and 7, preferably between 3 and 6, such as 3, 5, 6 and the like. The RF power applied to the base is less than 500W, and in the preferred embodiment, the RF power applied to the base is in the range of 50-200W. The ratio of the parameters is set, so that the surface can be deposited to form a high-density and low-roughness aluminum oxynitride film, the high-quality surface can inhibit a transition layer from being formed between the etching layer and the metal, and the oxidation of the metal layer is reduced.

FIG. 2 shows a graph comparing the number of particle defects in oxide thin films prepared according to an embodiment of the present invention and the prior art. FIG. 3 shows a graph comparing etch uniformity of oxide films prepared according to an embodiment of the present invention and prior art. Referring to fig. 2 and fig. 3, it can be clearly seen that the particle defects in the technical scheme are significantly reduced, the number of particles larger than 30 nm in the film on the wafer is within 5, and the uniformity of the wet etching is also greatly improved, and is reduced from 12.49% to 2.24%.

While the above description has been made by taking the formation of aluminum oxide and oxynitride films as examples, it should be understood that the method of the present invention may also be used to produce other films, such as composite films for the production of titanium, silicon, hafnium, or tantalum oxides and oxynitrides.

The invention reduces the oxygen proportion in the process, reduces the generation of particle defects in the deposition process of the metal oxide by using radio frequency/direct current co-sputtering on the target, and simultaneously deposits the nitrogen oxide film in the process to inhibit the water, oxygen and carbon in the air from adsorbing on the surface of the metal oxide to generate the particle defects. The target is added with a radio frequency power supply to increase the collision ionization of oxygen in plasma, change the distribution of oxygen atoms and improve the uniformity of wet etching of the oxide film. The invention increases the control mode of ion energy and distribution in the film growth process, enlarges the process window and provides a method for preparing the high-density oxide film.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (9)

1. A method for producing an oxide thin film, comprising:

step 1: putting a wafer to be deposited with a film on a base of a reaction chamber;

step 2: introducing mixed gas of argon and oxygen into the reaction chamber, applying direct current power and radio frequency power to the target material to enable the mixed gas to form plasma, and bombarding the target material by the plasma to form an oxide film on the wafer; the target is an aluminum, titanium, silicon, hafnium or tantalum target, or a compound target of aluminum, titanium, silicon, hafnium or tantalum;

and 3, step 3: stopping applying power to the target, introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying radio frequency power to the base to enable the mixed gas to form plasma, and bombarding the oxide thin film by the plasma to form a nitrogen oxide thin layer;

and 4, step 4: and (3) continuously introducing mixed gas of argon, oxygen and nitrogen into the reaction chamber, applying direct current power and radio frequency power to the target, and continuously applying radio frequency power to the base to enable the mixed gas to form plasma, wherein the plasma bombards the target and the nitrogen oxide thin layer formed in the step (3) to form a nitrogen oxide thin film on the nitrogen oxide thin layer.

2. The method according to claim 1, wherein the process conditions in step 1 are: the vacuum degree of the reaction chamber is less than 5E-6 Torr; the temperature of the base is 250-350 ℃.

3. The method of claim 1, wherein in step 2 and/or step 3, the flow rate of argon is less than 500 seem and the flow rate of oxygen is less than 500 seem, wherein the flow rate of argon is greater than the flow rate of oxygen.

4. The method of claim 1, wherein in step 2, the DC power applied to the target is less than 10000W, and the RF power applied to the target is less than 3000W, wherein the ratio of the RF power to the DC power is 2-4.

5. The method according to claim 4, wherein in the step 2, the DC power applied to the target is 100-200W, the RF power applied to the target is 300-600W, and the ratio of the RF power to the DC power is 3.

6. The method of claim 1, wherein in step 4, the target is applied with a DC power less than 10000W and the target is applied with a RF power less than 3000W, and the ratio of the DC power to the RF power is 2-7.

7. The method according to claim 6, wherein in the step 4, the DC power applied to the target is 3000-6000W, the RF power applied to the target is 1000-2000W, and the ratio of the DC power to the RF power is 3-6.

8. The method according to claim 1, wherein in step 3 and/or step 4, the sum of the flow rates of oxygen and nitrogen is greater than the flow rate of argon.

9. The method of claim 1, wherein in step 3 and/or step 4, the RF power applied to the pedestal is less than 500W.

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